Electronic and Magneto-Transport Across the Heusler Alloy (Co2FeAl)/p-Si Interfacial Structure

Abstract

Electronic and magneto-transport across the Heusler alloy Co2FeAl (CFA)/ p-Si structure have been studied. The morphology of the Heusler alloy film surface has also been characterized by atomic force microscopy and magnetic force microscopy (MFM). X-ray diffraction data revealed formation of the CFA alloy phase with the L21 structure. MFM results revealed formation of a fine domain structure of average size ∼10 nm and magnetic signal strength 0.23°. The I–V characteristics are strongly temperature-dependent between ∼80 K and 300 K for forward bias, compared with weak temperature dependence on reversing the polarity. At low temperature the I–V characteristics have the features of a backward diode. The observed strong temperature dependence is because of thermionic emission of carriers across the interface. The weak temperature dependence is because of dominant field-emission tunnelling of carriers across the interface. Large magnetic field sensitivity of the reverse current has also been observed. The observed magnetic field sensitivity for the reverse current shows the involvement of electronic spin in transport across the interface, from the Heusler alloy to the silicon. An MR of ∼35% in the presence of a magnetic field was estimated from the I–V data. The study has shown that spin-dependent tunnel transport from the CFA alloy to silicon across the interface results in the observed value of MR, which seems to be because of spin scattering.